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Phenotypic and genomic responses to titanium dioxide and cerium oxide nanoparticles in Arabidopsis germinants
Citation:
Tumburu, L., C. Andersen, P. Rygiewicz, AND J. Reichman. Phenotypic and genomic responses to titanium dioxide and cerium oxide nanoparticles in Arabidopsis germinants. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. Society of Environmental Toxicology and Chemistry, Pensacola, FL, , 14, (2014).
Impact/Purpose:
Engineered nano particles (ENPs) are being incorporated in numerous consumer products and used in various medical applications that will result in release of ENPs to the environment. Nano-titania (TiO2) is widely used in consumer cosmetics and sunscreens, foods, paints, and surface coatings of numerous materials. A likely route of environmental exposure is through application of sludge from waste water treatment plants to agricultural fields. Nano-ceria (CeO2) is a catalyst used in diesel fuels, incorporated in paints and other coatings, and is thought to enter the environment through areal deposition. The potential risks of these two ENPs are largely unknown, raising environmental and regulatory concerns at the national and global levels. Arabidopsis thaliana germinants were exposed to 500 mg NPs L-1 of nano TiO2 and nano CeO2 in separate experiments, and effects on gene expression and early growth and development were studied. Twelve days after exposure, nano-titania and nano-ceria resulted in significant changes in 204 and 142 genes, respectively [expression difference > 2-fold; p < 0.05 (t-test)]. The changes induced by these ENPs included genes related to abiotic (oxidative stress, salt stress, water transport) and biotic (respiratory burst as defense to pathogens) stimulatory responses. Further analysis of all the differentially expressed genes revealed that both ENPs affect a range of metabolic processes (DNA metabolism, hormone metabolism, tetrapyrrole synthesis, and photosynthesis), which are vital for plant growth and development. Both ENPs appeared to promote early germinant growth (emergence of radical, hypocotyl and cotyledon, and leaves). Although a relatively small portion of the genome was affected, the data clearly indicate that both ENPs have the potential to influence physiological processes in plants. The study shows that characterizing changes in gene expression provides a sensitive method for assessing non-lethal effects of ENPs on plants, and may lead to better screening protocols for assessing the toxicity of new ENPs as they are developed.
Description:
The effects of exposure to two nanoparticles (NPs) -titanium dioxide (nano-titania) and cerium oxide (nano-ceria) at 500 mg NPs L-1 on gene expression and growth in Arabidopsis thaliana germinants were studied using microarrays and phenotype studies. After 12 days post treatment, nano-titania and nano-ceria exposure resulted in significant changes in 204 and 142 genes, respectively [expression difference > 2-fold; p < 0.05 (t-test)]. The genes induced by these NPs include mainly ontology groups annotated as stimuli responsive, including both abiotic (oxidative stress, salt stress, water transport) and biotic (respiratory burst as defense to pathogens) stimuli. Further analysis of all the differentially expressed genes revealed both NPs affect a range of metabolic processes (DNA metabolism, hormone metabolism, tetrapyrrole synthesis, and photosynthesis), which are vital for the plant growth and development. Phenotype observations revealed both NPs promoted growth (emergence of radical, hypocotyl and cotyledon, and leaves) in germinants. The data clearly indicate that although molecular mechanisms of these two NPs are distinct despite some overlap in gene expression with respect to stress response, both NPs induce suites of genes related to various developmental processes that resulted in enhanced germination and growth of germinants.